With an increasing interest in sustainable energy production there is a focus on using photovoltaic arrays for producing electric power. Photovoltaic (PV) arrays include at least one photovoltaic (PV) cell, which is also known as a solar cell. Since the output voltage of one cell is relatively low, a PV array usually includes a string with a plurality of series connected solar cells or even several such strings connected in parallel.
As it is known, a solar cell, and thus a PV array, acts like a power generator providing a DC output voltage and a DC output current when it is exposed to sunlight. For a given light power received by the PV array there is a range of output currents and a range of corresponding output voltages at which the PV array can be operated. However, there is only one output current and one corresponding output voltage at which the electric power provided by the PV array has its maximum. The output current and the output voltage at which the output power assumes its maximum define the maximum power point (MPP). The MPP varies dependent on the light power received by the array and dependent on the temperature.
Maximum power point trackers (MPPT) are circuits that detect the maximum power point of a PV array and operate the PV array in its MPP independent on the voltage or current requirements of a load that is supplied by the PV array.
For providing higher output voltages a plurality of PV modules, with each module including a PV array and an MPPT, can be connected in series. In such a system with a plurality of series connected modules the MPPT in each module provides for the operation of the corresponding PV array in its MPP. An MPPT usually includes a switched-mode converter. A switched-mode converter includes at least one switch, like a transistor, that is operated at high switching frequencies, which are usually in the range of at least several kHz. Inevitably, the switching operations result in switching losses in the MPPT.
There is, therefore, a need for a circuit arrangement with a maximum power point tracking capability and with low losses.